Mucins are the primary secretory component of salivary mucous glands, such as the major sublingual gland and many of the minor salivary glands. Protective functions which have been attributed to mucins, include: 1) lubrication and hydration of oral surfaces; 2) selection for the adherence as well as clearance of specific micro-organisms; and 3) modulation of the pellicle lipid content through either covalently-bound fatty acids or through non-covalent, heterotypic complexation. within mucous glands, mucins are synthesized and secreted by the mucous cell phenotype. We propose to develop cell lines which express the raucous cell phenotype. For our studies we plan to use the rat sublingual gland. This gland is highly endowed with mucous cells and is very similar, both in morphology and in its pattern of innervation, to human mucous glands. Moreover, we are currently using acute preparations of rat sublingual mucous acini to determine secretagogue regulation of mucin secretion and to characterize secreted mucin. These results will provide a standard upon which to evaluate the level of differentiation of derived cell lines. The study of the molecular mechanisms which regulate the synthesis and secretion of mucins have been hindered by the cellular heterogeneity of salivary mucous glands which greatly complicates the isolation and study of cell-specific molecules and intracellular reactions. Therefore, to enhance the study of mucous cell biology, we will develop an immortalized cell line which displays the following characteristics: 1) Proliferate at a rapid rate and undergo serial passage without significant changes in growth characteristics; 2) Undergo induction to express the mucous cell phenotype as determined by: (a) the expression of transcripts and the synthesis of proteins specific for mucous cells; (b) the synthesis of mucin glycoprotein with biochemical characteristics similar to native rat sublingual mucin; (c) the expression of ultrastructural features characteristic of mucous cells (i.e. secretion granules containing mucous cell-specific secretory proteins, such as mucin); and 3) secretion of mucin in response to appropriate agonists. A differentiated mucous cell line would ultimately be used to study factors that control mucous cell-specific gene expression and to determine the coupling between the transcription and secretion of mucin. Such a model system would also greatly facilitate the elucidation of the molecular mechanisms involved in the intracellular pathways that regulate agonist-induced mucin secretion.